Skin Cancer

What Is Skin Cancer?


Skin cancer is a disease in which skin cells grow abnormally. In healthy skin new cells develop all the time to replace older cells. These normal new cells multiply and grow in an orderly way.

If skin cells grow out of control they form a mass or ‘tumor’. 

A skin tumor is considered benign (not cancer) if it is limited to a few cell layers and does not invade surrounding tissues or organs. But if the tumor spreads to surrounding tissues it is considered malignant or cancerous. 

Most skin growths are benign (not harmful).

There are 3 different types of skin cancer. They are different because they arise from one of the 3 different types of cells in the outer layer of the skin (see below to read about the different types of cells).

Each kind of skin cancer has its own distinctive appearance. Certain skin cancers also tend to develop in specific areas of the body.

The 3 different types of skin cancer:

  • 1. Basal cell carcinoma is the most common kind of skin cancer. More than 90 per cent of all skin cancers in the United States are basal cell carcinomas. Fortunately, basal cell carcinoma also is the least serious kind of skin cancer. That’s because it grows slowly and rarely spreads. It spreads in less than 1 out of every 1,000 patients.
  • 2. Squamous cell carcinoma is more serious because it does spread to vital organs inside the body. Spread occurs in a few cases in every 100. It does so slowly. At first cancer cells tend to spread only as far as the nearest lymph nodes structures, which filter out and trap the cancer cells. If spread has occurred, the affected lymph nodes can be removed before cancer spreads to vital organs.
  • 3. Malignant melanoma is the most serious kind of skin cancer because it may spread quickly from the skin through the lymph nodes or blood, to internal organs. For more information about melanoma, go to Melanoma.

To read about ‘What causes skin cancer?’ please go to ‘what causes skin cancer?’  

Understanding the skin and the cells that can become cancer:

The skin is made up of 3 three layers:

Epidermis – the outer layer of skin

Dermis – the middle layer of the skin; contains nerves, blood vessels, sweat glands, hair follicles, and oil-producing cells that keep the skin from drying out

Fatty layer – the deep layer of skin


Skin cancer begins in the outer layer of skin, in the epidermis.

The epidermis is made up of 3 types of cells and the names of these cell types gives the name to the type of tumor.

Squamous cells are cells that progressively flatten and fill with protective keratin (a tough, insoluble protein that makes skin almost completely waterproof) to form the outmost surface of the skin. These cells may give rise to sqamous cell carcinoma

Basal cells are small cells located at the base of the epidermis that serve as a reservoir for squamous cells shed from the skin. They can give rise to basal    cell carcinoma

Melanocytes are cells that produce a dark material, or pigment, that gives the skin its color. They can give rise to melanoma.


Facts about skin cancer

  • About 1.3 million Americans are diagnosed with skin cancer each year.
  • There are three kinds of skin cancer. The rarest, melanoma, is the most serious.
  • Almost half of all Americans will have some type of skin cancer at least once by the time they reach age 65.
  • Most cases of skin cancer occur in people age 50 and over.
  • Childhood sun exposure may decide an individual’s risk of skin cancer.
  • People with certain skin types have the highest risk of skin cancer.
  • Some individuals may inherit a defective gene that increases the risk of malignant melanoma.
  • The risk of skin cancer may be rising because of damage to Earth’s protective ozone layer.
  • A routine skin self-examination is important in early detection of skin cancer.
  • The cure rate for skin cancer would be almost 100 percent if all were detected early and treated.

Understanding Cancer

The body is made up of different types of cells that normally divide and multiply in an orderly way. These new cells replace older cells. This process of cell birth and renewal occurs constantly in the body.

‘Cancer’ is the name for a group of diseases in which certain cells in the body have changed in appearance and function. Instead of dividing and growing in a controlled and orderly way, these abnormal cells can grow out of control.

A tumor is considered benign (not cancerous) if it is limited to a few cell layers and does not invade surrounding tissues or organs. But if the tumor spreads – or has the potential to spread – to surrounding tissues or organs, it is considered malignant, or cancerous.

Cancer (malignant growths) occur when:

  • Some cells in the body begin to multiply in an uncontrolled manner.
  • The body’s natural defenses, such as certain parts of the immune system, cannot stop uncontrolled cell division.
  • These abnormal cells become greater and greater in number.

Who is most at risk of developing skin cancer

Anyone can get skin cancer. Although most cases occur in people over age 50 with fair skin, it can develop in younger people, and those with dark skin. In general, an individual’s lifetime exposure to UV light determines his risk.

Certain individuals have a risk that is higher than the rest of the population. Included are people who:

  • Have light skin that freckles easily and tends to burn rather than tan. Individuals with blond or red hair and blue or light gray eyes often have fair skin. The skin type table can help determine an individual’s risk.
  • Live in geographic regions closer to the equator, where sunlight is strongest. Residents of Florida, Texas, and southern California, for instance, have a greater risk than those in Maine, Wisconsin, and North Dakota.
  • Work outdoors or spend lots of time in leisure activities in the sun.
  • Already have had skin cancer. A diagnosis of skin cancer means that an individual has a higher-than-normal risk for the disease. These individuals must take great care to minimize UV exposure and follow other preventive measures.

The risk of skin cancer also varies with the kind of sun exposure.

  • Basal cell carcinoma and squamous cell carcinoma are more common in people who spend a lot of time in the sun over many years. This includes people who work outdoors or engage in other daily outdoor activities in warm climates.
  • Malignant melanoma is more common in people who get occasional, high-intensity sun exposure. People who sunbathe on vacations or during brief sunny periods in cold climates may get such exposure.
  • Some studies show that a single serious sunburn can increase the risk of skin cancer by 50 percent.


Nice To Know:

An adult’s risk of skin cancer may be decided during childhood. Most people get the majority of their lifetime sun exposure before reaching 18 years of age.










Always sunburn, don’t tan

Fair-skinned & freckled

Blue-eyed, Celts

Very High


Always sunburn

Tan minimally

Fair-skinned, blonde haired,

Blue-eyed, Scandinavians



Sometimes sunburn,

Tan moderately

Fair-skinned, brown hair,


Unexposed skin is white



Seldom sunburn,

Tan easily

Light brown skin, dark brown

hair, brown-eyed;

Unexposed skin is tan;

Mediterranean, Hispanic



Rarely sunburn,

Tan profusely

Brown skinned; darker

Mediterranean, Orientals,

Eastern Indians

Very low


Never sunburn,

Deeply pigmented



* Generally based on first exposure to summer sun following winter without exposure


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